The present disclosure relates to subject matter contained in Japanese Patent Application No. 10-210493 (filed on Jul. 27, 1998), which is expressly incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to a high-frequency snare that is removably inserted into an instrument-inserting channel of an endoscope to carry out excision of a polyp or the like in a body cavity.
2. Description of the Prior Art
In general, a high-frequency snare for an endoscope is arranged as illustrated in FIG. 9. A single electrically conductive elastic wire is bent into a U-shape at the distal end thereof and looped at the rear of the U-shaped bent portion to form a wire loop 93. The rear end of the wire loop 93 is connected to an electrically conductive control wire 92 axially movably inserted in an electrically insulating sheath 91. When the control wire 92 is pushed from the proximal end of the sheath 91, the wire loop 93 projects from the distal end of the sheath 91 to expand in a loop shape. When the control wire 92 is pulled, the wire loop 93 withdraws into the distal end of the sheath 91 to contract.
As illustrated in FIG. 10, there is another conventional high-frequency snare for an endoscope in which a distal end tip 95 is secured to the bent end portion of the wire loop 93.
However, in the high-frequency snare for an endoscope in which a loop is formed simply by bending an elastic wire as shown in FIG. 9, when a polyp is caught in the wire loop 93 and pinched tight therewith, large stress concentration occurs at the bent end portion 93a in the expanding direction. Therefore, there are not a few cases where when the high-frequency snare is repeatedly used, the bent end portion 93a is deteriorated and broken.
In the high-frequency snare in which the distal end tip 95 is secured to the distal end of the wire loop 93 as shown in FIG. 10, when the wire loop 93 expands and contracts, stress concentration occurs at the boundary A between the loop portion of the wire loop 93 and the secured distal end portion thereof. Therefore, it is also likely that the portion A of the wire loop 93 will be deteriorated and broken when the high-frequency snare is repeatedly used.